On The Same Side of Darkness
by Mio-san
Summary: He's a demon. She's a nekomata. It never should have been... but it was, and now, so many years later, Ari returns to the human world to find her previous acquaintance at the beck and call of a human. Will she and Sebastian rekindle their romance, or will they remain rivals, fighting for a certain soul on the same side of darkness? Rating subject to change, SebastianxOC
1. Journey

I pursued my brilliantly scarlet-colored lips in concentration, staring intently at the tiny bead of crimson balancing on the tip of my finger. "_Heal. _Reverse. Stay. You do not bleed. You are invincible. You do not bleed…"

"Hey, Ari."

"Ah!" I jumped, and my surprise broke the spell. The drop of blood trailed down my finger, pooling in the creases of my palm. I sighed and glared up at the mischievous-looking girl in front of me, hovering two inches off the ground. "What's up?" she asked, baring her fangs in a smile.

"Not now, Kira," I told her, lapping up the blood that was now sliding down my wrist. It was a cool, somewhat pleasant sensation. "Immortality isn't easy when you're physically mature but you still bleed when wounded like a common child."

Kira groaned, flapping her bat-like wings in irritation. "Tell me you're still not obsessing over that. It comes in time, remember? Besides, demons bleed, and they're pretty dang powerful."

"_Demons,_" I said, gritting my teeth, "are careless, arrogant good-for-nothings that are no better than the gods themselves. I wish you'd stop talking about them, they're not even cute."

"This coming from the nekomata that dated a…" Kira began, but I cut her off. "I already told you, _never _talk about that again. I made a mistake and I'm not making it again."

"Fine, whatever," Kira smirked, obviously not taking my word for it. I clenched my jaw even tighter, ignoring the sting of pain as one of my razor-sharp fangs scrapes the inside of my cheek. "Think what you want to think. He and I are never again. Trust me."

"Then…" Kira's voice reached a high pitch and I looked up worriedly. Her high voice never meant good news for me. "You probably won't want to hear about the new soul craze."

"Soul craze?" My raven-black nekomata ears pricked up, twitching on top of my head. "Really?"

Kira nodded solemnly. "Another revenge-hungry brat called on a demon and everyone's saying he has the most _delicious _soul…" She sighed blissfully. "_Everyone's _going to Earth to check it out. I can't, since I'm on probation."

"If you hadn't bitten that guy…" I reminded her, and the chimæra waved away the subject. "Whatever. The point is, I _would _send you down there, but…"

"But what? But what?" I was practically drooling. I hadn't consumed a soul in the longest time… they were getting harder and harder to obtain with those dang shinigamis.

"There's a catch," Kira warned.

"_I don't care_!" I practically moaned. "I'm _hungry…_"

Kira smiled again, a devilish smile. "Well, if you insist. There's a catch—for you, at least. The kid's demon…"

My heart dropped through my chest, down to my toes, through the floor and straight into the ground. "You're kidding."

"It's _him_," Kira confirmed.

"Aaahhh! _Dangit_!" I hissed aloud, something I didn't usually do because of the action's childishness, but it was very satisfying. "You've got to be kidding me! I can't believe it's him, of all demons! Stupid—ignorant—selfish—inconsiderate—I'm gonna kill him—" With each harsh remark, I slammed my fist down onto the rock I was sitting on. "_Unbelievable_—I'll have _words _with him—"

"Whoa, whoa, calm down!" Kira flapped a little higher to avoid my long, forked tail that whipped back and forth in agitation. "Look, you're smart. I bet there's some way you can get a little bit of soul without that demon breathing down your neck."

I shuddered at her imagery. "Sure, I guess. But how am I supposed to do that? Lure him away? You know how demons are with contracts. Especially if they're hungry."

"You're his ex-girlfriend," Kira pointed out, and I bit my lip. "He's gotta still have _something. _You're a nekomata, for heck's sake! You're a _catch_! Just use that to your advantage!"

I relented. "You've got a point. Okay, when's the next express teleportation to the human world?"

Kira looked up, momentarily consulting her inner schedule that all of us underworld creatures had. "Looks like… half an hour, maybe less."

"Dangit," I grumbled, and got to my feet. "I'm off now, then."

"Right now?" Kira repeated. "As in _right _now?"

"Course," I said carelessly, flipping long, layered hair over my shoulder. "Wouldn't want to miss out on a feast."

"Can't I come with you?" Kira whined. "You can smuggle me in!"

"Sorry, chimæra," I smirked. "This one's all mine, if I can help it." Ignoring the scowl on her face (and let me tell you, Kira's scowls are downright scary), I took off running, using every ounce of speed I had inside me to race off towards the Tele-Port. Black, volcanic landscape zoomed past, giving me that warm, cozy feeling one always gets when they're in their home. The endless, navy blue sky and electric green grass was enough, but add in the pristine lakes, towering mansions and never-ending night, and it was all that someone like me could ever want.

Why, you ask, would the underworld be so pleasant?

That's an easy one.

It's temptation.

Temptation is the source of evil, as believed by many of us nightmarish creatures. If an average human was given the choice between heaven and here, they'd choose the latter for its paradise-like appearance. Naturally, they'd regret it in about two seconds when we devoured their soul. Still, when an occasional fool came along, it was nice for us to enjoy a little meal. And besides that, who _wouldn't _want to live here? According to Kira, it was packaged-up paradise on the Other Side. What the Other Side was, I didn't know. Apparently it was some human term.

Anyway, about the Tele-Port. We creatures of the night needed some way to get to the human world when we were ready for a little soul pick-me-up, so some of the smarter demons (gag) came up with a way. With the Tele-Port, we could blink into and out of dimension whenever we wanted, as long as we were wearing a transmitter. My transmitter was disguised as an earring on my right ear. Kira wore hers as a pinky ring.

The only catch to the Tele-Port was since Earth's magnetic field (advanced demon intelligence—"Earth is the center of the universe" is _so _last century) was so strong, we needed to be at a station to blink out of the underworld. Luckily, there was one close by, but I wanted to get to the human world fast and all the express trips were done at certain times of day, in groups. That was why I was running as fast as I could, blowing through my fellow underworld-dwellers like lightning. Ignoring irritated looks and grumbling, I sped up, trying to keep my energy level soaring. Just in time—there was the station, with a queue of varied horrific creatures straight out of some kid's nightmare waiting to be teleported. I barely managed it onto the platform as it geared up, humming loudly. Sparks like risen from a fire swirled around us at an incredible speed, blurring into light that obscured my vision. I kept my eyes open, calm as the rest of them, as I had done this before. Slowly, then faster and faster, a spinning sensation surrounded me, until I fell back onto a pillow of air and slipped into unconsciousness as my body and mind traveled between dimensions.


	2. Arrival

My eyes flew open; just in time, as my image flickered and solidified and my feet touched down on the grass. "Perfect," I said out loud, checking my surroundings. Sure enough, here I was—Victorian Era England. _Kira was right. I can practically _taste _that delightful little soul._

Naturally, courtesy of the Tele-Port, I was crouched behind a row of bushes. Lucky thing, too, I realized, as I looked myself over. A short-ish black skirt and a lacy top with stiletto heels wouldn't do at all for a "lady", as they called someone like me here in the human world. With a snap of my fingers, my attire morphed into an elegant black dress with long, draping sleeves, a skirt that danced around my feet, and a neckline with sheer fabric that crept up to my neck and ended at a pearl choker that fit gracefully around my neck. "That's better," I said out loud, and stepped out from behind the shrubbery, as if noblewomen emerged from gardens everywhere in the world (they don't). My nekomata ears and forked tail dissolved, leaving me with a strange feeling of emptiness. That was virtually the only part I didn't like about visiting Earth—apparently cat-people cause quite a stir.

That's apparently, if anything.

Still, it was necessary, and I lamented it as much as the next person, but there was nothing to be done about it. After I feasted on a soul, I could go back to the underworld and enjoy as much time with my beloved nekomata features as I wanted. So instead of delaying it any longer, I set off down the street, checking my internal compass that yes, all creatures of the night had. "Looks like I'm headed to the Phantomhive estate," I murmured, and smiled. The tiniest hint of a fang peeked out from my lip.

It took me almost no time to reach the manor's gate, though I was guessing that my speedwalking was a lot faster than most people's running, being a nekomata and all. With a flick of my hand, the gate flung open, and I strode through, keeping a wary lookout for guards, sharpshooters, or exploding flowers. It's happened. Plus, I didn't like being shot. It had this strange ticklish sensation…

Nevertheless, no one was around, which puzzled me. Still, better not to question luck. I ascended the stairs leading up to the mansion's front door and raised my hand to knock, still somewhat wary. This was strange… all too strange.

Ah, wait. There it was.

In a blur of motion, a bullet came barreling towards me. I sidestepped easily, letting it shoot past and bury itself in the pavement behind me. There was a shout from the rooftop, followed by a "take your glasses off, Mey-Rin!" and a responding "sorry, sorry!"

I held my hands up in surrender, widening my eyes for that impression of innocence. "Please don't shoot! I'm unarmed!"

Whispers immediately rose. I strained my human ears, cursing their lousy ability to pick up vibrations. A full minute passed, and then three heads peered over the rooftop with curious expressions on their faces. The first voice, belonging to a man with blond hair and blue eyes, piped up. "Oi, sorry 'bout that. Gotta keep the master safe, eh, Mey-Rin?"

The girl next to him, with magenta-colored hair done up in pigtails and thick glasses perched on her nose, nodded violently. "Got to check who's come knocking, yes!"

Trying to overcome the strangeness of the fact that three people were shooting at me from on top of a roof, I craned my head and looked back up at them. "I'm looking for Earl Phantomhive," I shouted up. "Is this the Phantomhive estate?"

"This is the place!" the third one chirped. He was a boy of about sixteen with blond hair and teal-colored eyes. "I'm Finni, and this is Bard, and Mey-Rin. We're the servants!"

_A little perky, no? _I thought, while maintaining my childishly naïve grin. "Nice to meet you, Finni, Bard, and Mey-Rin. Er… do you mind if I come in?"

The three servants promptly disappeared behind the rooftop, and not thirty seconds later the door flung wide. I jumped back to avoid getting clipped by its wooden edge, then stepped back, easily regaining my balance. The servants stood at the door, leaving me wondering how on Earth they had gotten down to the main level so fast. "Please come in, yes!" Mey-Rin said, gesturing me in. "Welcome to the manor!"

I stepped inside, taking in my surroundings. It wasn't nearly as nice as the mansions we had back in the underworld, but I had to admit that it was pretty beautiful considering it existed in the human world. The foyer was especially impressive, what with the double staircases and flower bouquets. Not that I was impressed. Not at all. It was boring, really.

And then a door swung open at the top of the staircase, and there _he _was. Stuck fast like a shadow to… Ooohh, and enter the reason I was here. That tasty little soul… I could smell it from here. I licked my lips involuntarily, anticipating the delicious meal that lay in front of me.

"Who are _you_?"

Biting words sliced through my fantasy and I scowled, glaring up at the demon I knew _too _well and his small master. "Excuse me?"

The Earl Phantomhive shot me an equally sour expression. "I _said, _who are you?"

"Now, now, young master," a deeper, smoother voice soothed. "Be polite to our guest."

I looked up into his eyes for the first time in two years. They were as deep and as crimson as ever, and his mouth curled into a devilish smile as he stared at me from the top of the staircase, like the high-and-mighty demon he thought he was. "And to whom do we have the pleasure of hosting?"

I choked down my resolve and raised my gaze to a cold, level stare. "My name is Ari. I have matters I'd like to discuss with the Earl."

The latter crossed his arms and met my stare with his own. "Sebastian, do you know her?"

I stifled a smirk. _Sebastian, huh? Could it be that this little brat really does have a demon wrapped around his finger? Impressive. Especially considering _he's _the demon._

Meanwhile, "Sebastian" had leaned down to the boy's level. "I'm afraid I've never seen her before."

_Moron. _I clenched my fist, then buried it in the silk folds of my dress. "No matter," I purred, all charm. "Shall I come back another time? It is—" I paused and glanced out the window—"getting dark. I shall just walk home alone."

The Earl and his butler conversed quietly for a few moments, then they straightened and both looked me in the eye. "You will be allowed to stay for the night, as long as your business is worth it. I'm very busy, after all."

"Oh, please don't worry, my lord," I chirped, staring straight into Sebastian's soulless demon eyes. "I will wait as _long _as it takes."


	3. Alone

Oh, it was _killing _me!

My fingers flexed as Sebastian smiled at me. "Wonderful to know. Shall I escort the lady to her bedroom?" This was to the young Earl.

He nodded, sighing. "Might as well. We can conduct business in the morning. I'll be waiting, Sebastian." The Earl slipped through a door on the right and disappeared, and I ascended the stairs eagerly. _Please let my bedroom be through there… Heck below, I'm _starving_!_

Naturally, Sebastian led me off into a darker corridor in the opposite direction. I gritted my teeth and suddenly there he was beside me, still smiling. "I do hope the lady is not afraid of the dark."

I actually yelped a little, to my eternal embarrassment. "Of course not. I live for the dark."

The demon's smile grew wider. "I should hope so. Fortunately, this mansion does not lack in darkness." I felt a hand brush against my own.

My eyes narrowed until they were tiny slits. How _could _he? After being such an utter jerk to me, he didn't come out and apologize—not even close! Instead, he _taunted _me—practically had a feast right in front of me! Those moronic demons—they didn't know what it was like to starve. Since humans called on them all the time, they were _never _hungry, and then of course they had to go and make themselves better than anyone else, too. News flash: while demons lived it up in paradise lost, minor creatures like nekomatas were stuck in destination dystopia! I had never wanted to slap someone in the face so—dang—much.

Unfortunately, I didn't get that chance. With the click of a lock, Sebastian escorted me into a bedroom with a large four-poster bed as its centerpiece. I turned around and he was _right there_, practically an inch away. "Is there anything else I can do for the lady?" he asked. His voice was a deep, low purr.

My eyes glossed over. Heck, he was attractive, and we were so close, and _oh, _that purring voice—

_Purring. _Cat. Nekomata. _Hungry! _I snapped out of it. "No, nothing. Why don't you go back to your little human pet?" I was surprised at the stone-cold tone of my words.

The demon looked taken aback, then he smiled again. "Very well. If that is what you wish."

"'What you wish,' my _tail_," I snarled under my breath as he slipped out the door, closing it behind him. Kicking off my painfully tight shoes, I collapsed into bed. With a snap of my fingers, the dress morphed into a lacy black nightgown, and I exhaled heavily as the suffocating corset disappeared with it. Finally I could be myself without anyone watching—unless the mansion was equipped with a security system, and seeing as underworld technology was far more advanced than Victorian-Era junk, I was one hundred percent sure that I was alone.

With that said, was I really happy about it? Before that idiotic demon had come into my life, I was bored with myself. Living out my days in the underworld didn't sound too bad, but I wanted excitement in my life. The same routine every single day could get old _very _fast. I met Kira and for a while we spent time together, but she was a chimæra and didn't like to stay in the same place for a while. So I ended up lounging on the dark, sandy beach and staring out at the Sea of Immortality, sipping glass after glass of strawberry-flavored carbonation. The nekomata inside screamed for some action, but no one answered.

Until I met _him_.

He was enchanting, kind, handsome—everything a nekomata girl could want. We spent each night and every day together, and when I would get slightly doubtful of his dedication he would take me into his arms and whisper tempting promises in my ear, capturing the naïve girl I had once been.

Then one day a human summoned him, and he left for what would become five years. I waited every day for his return until that very day everything had changed—how silly I had been! He _was _a demon, after all. I should have known better than to fall for him, but I did… hard.

It wasn't necessarily a bad thing, of course, I mean, he was _very _attractive, and how I longed to be with him again…

I got up, walked into the hallway, found a bathroom to my right, filled a glass with water, and splashed it all over my face.

"_Aagh—eep!_"

_Shh!_

I slapped myself across the face, dropped the glass, and fell back against the wall, panting. What did I have to do to get that blasted guy out of my head! Was it some sneaky demon trick to invade my mind and create an obsession, or was I just… _no. _I was _not _obsessed. And I was certainly _not _going back on my decision.

_Really, _I thought to myself as I walked back down the hallway, shut the door to my bedroom, and clambered back into bed. _What is wrong with you? Didn't you learn your lesson two years ago?_

Two years to the day. How could I forget?


	4. Proposal

**A/N: It's aliiiiive!**

**Just kidding. The addition of author's notes to OTSSOD!**

**I know you're all ready to strangle me for not having updated in, er, forever, but to be fair, school is really taking its toll on me! Plus I've been sick… anyway, it's back, and I'd like to thank all of my readers for their support. **

**Also, the chapters will be longer from now on. I'm sorry about that, too. So thanks everyone and enjoy my new chapter!**

I was _seriously _annoyed.

The boy, Earl Phantomhive, and I sat opposite each other in the lounge while Sebastian (ugh) poured us cups of Earl Grey. "The young master's favorite," he explained as he set my teacup on the table. "I hope you find it enjoyable."

I took one sip of the tea and almost fell over. _Horrible-tasting—how do humans drink this stuff? Hmph, he must have done it on purpose._

"So?" The earl looked about as sour as I felt—or maybe that was just how he always looked. "What's this business proposal?"

I panicked, suddenly realizing I had nothing to say. I had to give myself some excuse to stay at the Phantomhive Manor… but what was I to do?! I was a nekomata, not a genius!

"I'm _waiting,_" Earl Phantomhive snapped, and Sebastian cleared his throat. "Give the lady a moment to gather her thoughts. We mustn't hurry her."

_Think… think… aha!_

"My lord," I said, digging my fingernails into my skin underneath the table, "the business world is full of many wonderful opportunities. Toys are merely the tip of the iceberg." (What? So I had done some research last night. Shoot me.)

The Earl looked mildly interested. "Go on."

"As you may know," I continued, "many of the most thriving industries today revolve around textiles and clothing. As a member of the general public, I would like to point out—"

"Forget it," the Earl interrupted. "I've already considered clothing as a product. The investment is far too much and far too risky."

"Young master," Sebastian chided. "The idea is well-worn, but not exhausted. Our guest has a point."

I stared at the demon like he had just allowed himself to be shot. Was he… _helping _me?

Oh, heck below, these creatures are so frustrating!

Eventually I realized that they were waiting for me to speak, and cleared my throat, folding my hands on top of the table in the most businesslike way I knew. "Clothing is a valuable industry. When you have such resources at your disposal as the Lord Phantomhive has, it is quite simple to manufacture and sell textiles. I would like to volunteer my services: I have quite a few ideas in the works, as one might say, and would be happy to assist you, should you agree."

The Earl looked from Sebastian to me. "It's… an interesting proposal. I will consider it. In the meanwhile, Miss…"

"Blackwood," I supplied.

"Miss Blackwood will be allowed to stay at my mansion for the time being," he continued, looking up at his butler. "Sebastian, you will treat this woman as an honored guest."

"Understood, my lord." Sebastian bowed. When he lifted his head, I caught a hint of a smirk on his face.

"Ouch!"

…

"Thank you ever so much for helping me," I said as charmingly as possible as the demon dabbed at my cut with antiseptic. "I become so nervous when speaking to a person of such high station, I suppose my nails were a little too sharp!"

"It's no trouble," Sebastian replied. "Anything for our _honored guest._"

We sat together in what I supposed to be some sort of home infirmary, me doing my best to keep from flinching as my cut stung. Sebastian continued to treat it, cradling my hand in his as I scowled and bit my lip.

Finally I spoke up once more. "So, what do you really want?"

He looked up at me, all innocence. "I beg your pardon?"

I yanked my hand away and stood, crossing my arms. "Oh, please. Drop the act. You and I both know you're after the child. But why waste your time? You could devour him in the blink of an eye. This is below you—but then again, demons are low creatures."

He made a _tsk tsk _sound, shaking his head. "Ah, Miss Blackwood. This could not possibly be about what happened so many years ago?"

Narrowing my eyes, I deepened my scowl. "No, of _course _not. This is about the meal you so obviously desire. I see you salivating over the kid's shoulder whenever he's around, why not just get it over and done with?"

"I don't know what you mean—_Ari_." Sebastian smiled patronizingly at me. "You are very well aware of the contract we demons abide to. Dishonoring that contract—now, I would never do such a thing."

I snorted. "Nice try. How gentlemanly of you. Regardless of what that freaking contract holds you to, I'm not about to stand around and—"

In a flash, he was within an inch of me, cradling my chin like a child. "Oh, Ari. So many years have passed, and yet you are still the naïve, beautiful nekomata I fell in love with."

"Who do you think you're calling—?" My heart stopped. "The nekomata… you fell in love with?"

"But of course." Sebastian let his lips brush mine, ever so gently. "Do you think, Ari, that my feelings for you evaporated within such a short time? You were always mine, and I was always yours. Give up these foolish desires and return to the underworld. Wait for me. I will return to you, and we may live out our days together."

"Together…" I could feel his breath on my cheek. Sure, he was probably playing me, but here's the thing about demons. They know want, and they know temptation. They were practically designed to lure you in. And, oh, I was being lured.

"Could we… could we really?"

"Of course." He laughed softly. "I love you, Ari, and I always have."

My eyes softened. And I leaned in…

And slapped him across the face.

He stumbled back and stared at me. I gave a sort of hysterical laugh. "_Pl-ease. _As if I would fall for that! You demons never change. Still lying, heartless players who can't feel love."

Sebastian stared for a moment more, then sighed and smiled. He looked up, straight into my eyes.

"Very well, Miss Blackwood," the demon butler said, giving a deep, sweeping bow. "If that is how you wish to play the game, I will be happy to oblige. Now, if you will allow me. Today's lunch is pigeon compote with onion custard, and the young master will be expecting you." He guided me towards the door. "You are, after all, our guest."

**A/N: Pigeon. Ewww…**

**In case you're wondering, that was an actual Victorian-era-type meal. I wonder if Sebastian caught them fresh from the garden… you know what? I'm overthinking it. I really need to get some sleep.**

**Anyway, did you guys likey? I'll be updating more soon!**


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